P0056 Code- HO2S Heater Control Circuit Bank 2 Sensor 2

Discussion in 'P - Powetrain Codes' started by fault code, Jun 15, 2017.

  1. fault code

    fault code Administrator Staff Member

    May 11, 2017
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    What Does Code P0056 Mean

    This code means that the bank 2 sensor 2 oxygen sensor is not heating up properly due to a problem in the oxygen sensor heater circuit.

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    Possible symptoms
    • Engine Light ON (or Service Engine Soon Warning Light)
    Possible causes
    • Faulty Heated Oxygen Sensor (H2OS) Bank 2 Sensor 2
    • Heated Oxygen Sensor (H2OS) Bank 2 Sensor 2 harness is open shorted
    • Heated Oxygen Sensor (H2OS) Bank 2 Sensor 2 circuit poor electrical connection
    • Heated Oxygen Sensor (H2OS) Bank 2 Sensor 2 circuit fuse
    • Faulty Engine Control Module (ECM)
    Troubleshooting P0056

    This code can only be caused by problems in O2 sensor heater circuit, or by the sensor itself.

    Typically, heated O2 sensors have four wires – two of which go to the heater circuit and two that are power and ground for the sensor. In this case study, we are only concerned with the heater circuit.
    Typical O2 sensor heater circuit and connectors
    (Courtesy: alldata.com)

    You’ll want to obtain the wiring diagram from your vehicle to be certain you are testing the correct wires.
    • Test the heater circuit wiring
    First, you want to disconnect the O2 sensor connector and test the heater circuit for power and ground. You can do this using a digital multimeter.

    By consulting the wiring diagram for you vehicle, determine which pin on the connector is power and which is ground. Set your multimeter to the volts setting.Touching the black multimeter lead to ground and the other to the power feed on the connector, you should see a reading that’s close to battery voltage. If not, you have a problem with the O2 sensor power supply. You’ll need to consult the power side of the wiring diagram to find where the circuit fault lies.

    To test the ground side of the circuit, connect the red multimeter lead to the battery positive terminal and the black lead to ground. Once again, you should see a reading of about 12 volts. If not, you’ll need to consult the ground side of the wiring diagram to find where the circuit fault lies.
    • Test the sensor heating element
    If you’ve got good power and ground, the next thing to do is check the sensor heating element for either high resistance or an open circuit. You’ll do this using your digital multimeter.

    Set your meter to the ohms setting. Then, connect your meter leads to both of the heater circuit pins on the sensor side of the connector. Consult the service information to see if the resistance value on your meter is within specification. If not, the heating element inside the sensor has high resistance and the sensor should be replaced.

    If you get a reading that says OL on your meter while performing this test, the heating element has an open circuit. Once again, in this case, the sensor should be replaced.
    Testing O2 heater element resistance
    (Courtesy: 2carpros.com)

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    Last edited: Jun 15, 2017

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